A compressor serves to convert mechanical energy into compressive energy of fluid. Compressors may be categorized into a reciprocating type, a rotary type, a vane type and a scroll type according to a compressing mechanism with respect to fluid.
The reciprocating compressor is provided with a driving motor for generating a rotational force and a compression unit for compressing a refrigerant, a fluid, by receiving a driving force from the driving motor, within a hermetic container.
The compression unit serves to compress the refrigerant by a reciprocating motion of a piston connected to a crankshaft by a connecting rod, in a cylinder. Currently, a variable capacity type reciprocating compressor which is capable of adjusting a compression capacity according to a size of a refrigerating load has been developing. A double-capacity reciprocating compressor (hereafter, abbreviated to “double-capacity compressor”) among the variable capacity type reciprocating compressor has the piston having a stroke that is variable according to a rotation direction of the crankshaft, and accordingly, operated in a power mode or a saving mode.
FIG. 1 is an exemplary view showing the related double-capacity compressor.
As shown, in the related double-capacity compressor, an eccentric portion 3 is formed at a crankshaft 2 of a driving motor 1 rotated in a forward direction and a reverse direction according to an operation mode of the compressor, and an eccentric sleeve 4 is rotatably and eccentrically coupled to the eccentric portion 1. Further, a connecting rod 5 is rotatably connected to the eccentric sleeve 4, and a piston 6 performing a rotary motion in a cylinder (C) is coupled to an end of the connecting rod 5.
A latching unit 7 is installed at the eccentric portion 1 of the crankshaft. The latching unit 7 is protruded by a centrifugal force and then stopped by a stopping ends 4a, 4b of the eccentric sleeve 4 so that the stroke of the piston 6 is variable according to the operation mode of the compressor.
In the related double-capacity compressor, when the crankshaft is rotated by a power applied to the driving motor, the latching unit 7 installed at the eccentric portion 1 of the crankshaft is protruded and then coupled to a first stopping end 4a or a second stopping end 4b of the eccentric sleeve 4 according to the operation mode thereof. And, the eccentric sleeve 4 is eccentrically rotated together with the crankshaft, accordingly the connecting rod 5 is rotated and the piston 6 coupled to the connecting rod 5 is reciprocated within the cylinder (C), thereby compressing the refrigerant.
Here, as shown in FIG. 2, in the power mode by which the crankshaft is rotated in the reverse direction (counterclockwise rotation), the piston 6 is reciprocated by two times a total eccentric amount (E+ε) obtained by adding an eccentric amount (E) of the eccentric portion to an eccentric amount (ε) of the eccentric sleeve so that the compressor can be operated by a maximum cooling capacity. On the contrary, as shown in FIG. 3, in the saving mode by which the crankshaft is rotated in the forward direction (clockwise rotation), the piston 6 is reciprocated by two times a total eccentric amount (E−ε) obtained by subtracting the eccentric amount (ε) of the eccentric sleeve from the eccentric amount (E) of the eccentric portion so that the compressor can be operated by a minimum cooling capacity.
However, the related double-capacity compressor is operated by the eccentric amount that is obtained by subtracting the eccentric amount (ε) of the eccentric sleeve from the eccentric amount (E) of the eccentric portion in the saving mode, accordingly an upper dead point of the piston 6 cannot reach the end (position where a discharge valve is located) of the cylinder (C). Accordingly, as shown in FIG. 3, a dead volume is generated, thereby limiting increasing a variable ratio of the cooling capacity.